Was "Atma" supposed to have a storyline?

[Roogle]

ultima... I was gonna pee in my pants when i readed its name. but it was too easy to win... but anyways. What i think about ultima, is that he is forming of multiple espers. He was in floating continent, and I am pretty sure nothing could have flewed it there.

and its second forme, i dont remember name, was imprisoned by kefka? why? Well maybe because kefta couldn't kill it? this is kinda hole in my esper theory, because if atma would have been esper, kefka would have killed it for magitite.
Maybe kefka wanted it to grew stronger before killing it?

I was under the impression that Ultima Weapon was a separate existence from the espers, and that it was sealed away until the rise of the Floating Continent whereupon it escaped and attacked the party as they wandered through it.